Devices such as mobile phone, digital AV apparatuses, integrated circuit cards, etc. have been improved to have higher performance, semiconductor silicon chips (hereinafter, refer to as chips) to be mounted in the devices consequently need to be smaller and thinner in order to greatly increase the number of chips mounted in packages of the devices. To greatly increase the number of chips mounted in the package, the chips needs to be thinned not more than 150 μm.
However, when semiconductor wafers (hereinafter, refer to as wafers) to be substrates of the chips are polished to a thin thickness, strength of the wafers are reduced. The thin wafers with weak strength are easy to be cracked or curved. Further, the thin wafers with weak strength are difficult to be transported by automatic transportation. This requires manual transportation, and thereby tedious handling.
To deal with this problem, a wafer support system has been developed to reinforce the strength of the wafers by adhering supporting plates (made from glass, rigid plastic, or the like) to the wafers before polishing. The wafer support system prevents cracking and curving of the wafers. The wafer support system, which reinforces the strength of the wafers, allows automatic transportation of the thin wafers.
The wafer and the supporting plate are adhered to each other via an adhesive tape, a thermoplastic resin, an adhesive, or the like. The supporting plate is stripped from the wafer before dicing. For example, in case where the wafer and the supporting plate are adhered to each other via an adhesive tape, the wafer can be torn off the supporting plate supporting plate. Meanwhile, in the case where the wafer and the supporting plate are adhered to each other via a thermoplastic resin, the thermoplastic resin is heated and dissolved so as to strip the wafer from the supporting plate. Further, in the case where the wafer and the supporting plate are adhered to each other via an adhesive, the adhesive is dissolved by use of a solution so as to strip from the wafer supporting plate adhering.
Further, an opposite surface of a surface adhering to the supporting plate of the wafer is sometimes adhered to a support such as a dicing tape in accordance with the film thickness of the wafer before the supporting plate is stripped from the wafer. Therefore, the wafer is supported by the dicing tape. Hence, the occurrence of a crack and the like can be reduced even if the film thickness of the wafer is thin and the strength thereof is low.
Further, as other examples of techniques for processing a wafer, Patent Literatures 1 and 2 disclose a laser processing for cutting a wafer into respective chips by irradiating a laser beam to the wafer in order to form the chips from the wafer. A protective film is formed on a surface of the wafer before the wafer is cut in order to prevent the wafer from receiving an influence of debris occurring when the wafer is cut by the laser during the laser processing.